In recent years, the higher integration of semiconductor devices has been required along with enhancement in the performance and miniaturization of electronic devices such as cell phones and IC cards. As a procedure for higher integration, the finer pattern of semiconductor devices themselves, and a stack structure in which semiconductor elements are stacked longitudinally have been investigated. In production of the stack structure, an adhesive is used for junction between the semiconductor elements.
In the production of the stack structure, flip chip bonding has been known as a method of mounting an IC chip on a substrate. This is a method in which a plurality of bumps (projected terminals) are provided on the IC chip and the bumps are electrically connected to electrode terminals on the substrate. An underfill agent is used to fill a gap between the substrate and the IC chip and protect the IC chip against moisture and an exterior stress. As the underfill agent, a composition containing an epoxy resin has been used (e.g., Patent Documents 1 and 2). Conventionally, a method has been mainly used in which the underfill agent is injected after the substrate and the IC chip are connected using the bumps (post-applying underfilling), and then thermally cured. However, miniaturization of the bumps, a decrease in pitch, and an increase in the size of the IC chip make post-applying of the underfill agent difficult. As a countermeasure, pre-applying underfilling will be mainly employed in the future in which before the wafer is diced the underfill agent is previously formed on a wafer with bumps, and then diced IC chips are used for flip chip bonding.
As an adhesive for bonding a semiconductor element, an adhesive composition containing an epoxy resin has been known (e.g., Patent Document 3).
A method for producing a semiconductor device of a wafer-on-wafer (WOW) structure has been known as another stack structure (e.g., Patent Document 4).
A thermosetting resin composition containing a compound having an aromatic benzoxazine ring in a main chain has been known (e.g., Patent Documents 5 and 6). A benzoxazine resin has been also known to have excellent heat resistance and electrical characteristics.